Start from a basic dress with darts with zero or positive wearing ease depending on the fit you prefer and the fabric you will use.
Our method for drafting perfectly made to measure basic blocks (contoured ones, and the ones with wearing ease) and for fitting them in our basic blocks course/module 1.

Trace full front, then draw the asymmetric neckline, the new armhole, the slash line on back and the new side seams discarding waist darts.

Here we manipulate the shoulder shifting the seam more towards front, where gathers will be.

Highlight pieces to be traced separate, then widen the short shoulder dart by 1cm at neckline to make it tighter to chest.